package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Component
@Slf4j
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;
    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }
    public void set(String key, Object value, Long time, TimeUnit unit) {
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        //设置逻辑过期
        RedisData redisData = RedisData.builder()
                .data(value)
                .expireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)))
                .build();
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }
    //缓存穿透
    public <R, ID> R queryWithPassThrough(
            String keyPrefix,ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1.从redis查询商户缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isNotBlank(json)){
            //3.存在，直接返回
            return JSONUtil.toBean(json, type);
        }
        //判断命中是否为空值
        if(json != null){
            return null;
        }
        //4.不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        //5.不存在，返回错误
        if(r == null){
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "",CACHE_NULL_TTL, TimeUnit.MINUTES);
            //返回错误信息
            return null;
        }
        //6.存在，写入redis
        this.set(key, r, time, unit);
        //7.返回
        return r;
    }
    //线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    public <R,ID> R queryWithLogicalExpire(
            String keyPrefix,ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit){
        String key = keyPrefix + id;
        //1.从redis查询商户缓存
        String Json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isBlank(Json)){
            //3.未命中，直接返回
            return null;
        }
        //4.命中，需要把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(Json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject)redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判惭是否过期
        if(expireTime.isBefore(LocalDateTime.now())){
            //5.1未过期，直接返回店铺信息
            return r;
        }
        //5.2已过期，需要缓存重建
        //6.1获取互斥锁
        String lockKey = key;
        boolean isLock = tryLock(lockKey);
        //6.2判断是否获取锁成功
        if(isLock){
            //6.3成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //6.4返回过期的商铺信息
        return r;
    }
    private boolean tryLock(String key) {
        //1.获取锁
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unLock(String key) {
        stringRedisTemplate.delete(key);
    }
}
